reflection- the bouncing back of a particle or wave that strikes the boundary between two media.
The picture above represents the difference between the reflection of particles and the reflection of waves.
totally reflected wave- when all the wave energy isreflected back along the spring rather than being transmitted into the wall. (see figure 29.1 in Conceptual Physics book)
partially reflected wave- when part of the wave energy bounces back along the first spring, while the other part travels along the heavy spring. (see figure 29.2 in Conceptual Physics book)
Chapter 29 Section 2 - The Law of Reflection
normal- a line perpendicular to a surface.
angle of incidence - angle between an incident ray and the normal to a surface.
angle of reflection- angle between a reflected ray the normal to a surface.
law of reflection- the angle of incidence for a wave that strikes a surface is equal to the angle of reflection. This is true for both partially and totally reflected waves.
angle of incidece = angle of reflection
The above image shows how the law of reflection works. Such that, the angle of incidence=the angle of reflection.
Chapter 29 Section 3 - Mirrors ~ On a mirror rays of light are reflected from the mirror surface in all directions.
~ The number of rays is infinite, and every one obeys the law of reflection. As described below the figures, these two images represent how light rays are affected when in context with a convex and concave mirror.
virtual image- an image formed through reflection or refraction that can be seen by an observer but cannot be projected on a screen because light from the object does not actually come to a focus.
The above image shows how a virtual image works.
Chapter 29 Section 4 - Diffuse Reflection
diffuse reflection- the reflection of waves in many directions from a rough surface.
~Reflection of each single ray obeys the law of reflection, the many different angles that incident light rays encounter cause reflection in many directions.
~We see most of the things around us by diffuse reflection. In the above image, light rays are hitting a rough surface and scattering in different directions. This represents diffuse reflection.
Chapter 29 Section 5 - Reflection of Sound ~An echo is reflected sound.
~Sound reflects from all surfaces of a room, such as: walls, ceiling, floor, furniture, and people.
acoustics-the study of the need to understand the reflective properties of surfaces.
reverberations- persistence of a sound, as in an echo, due to multiple reflections.
The above figures, though already described underneath the pictures, represents reverberation in a room.
Pictured above is the Davies Symphony Hall in San Francisco. Above the orchestra are shiny plates that reflect both light and sound.
Chapter 29 Section 6 - Refraction
refraction-the change in direction of a wave as it crosses the boundary between two media in which the wave travels at different speeds.
The above picture is a simple representation of how a refracted ray is refracted when hitting a different medium.
wave fronts- the crest, trough, or any continuous portion of a two-dimensional or three-dimensional wave in which the vibrations are all the same way at the same time.
Chapter 29 Section 7 - Refraction of Sound ~On a warm day, the air near the ground may be appreciably warmer than the air above.
~Since sound travels faster in warmer air, the speed of sound near the ground is increased.
~Sound waves will then bend away warm ground, making it appear that the sound does not carry well.
~On a cold dayor night, when the layer of air near the ground is colder than the air above, the speed of sound near the ground is reduced.
~The higher speed of the wave fronts above cause a bending of the sound toward the earth.
~When this happens, sound can be heard over considerably longer distances. The above and below images show the way warm and cool air affect how sound travels.
Chapter 29 Section 8 - Refraction of Light
~A pond or swimming pool both appear shallower than they actually are.
~A pencil in a glass of water appears bent.
~Wonder why?
~These effects are caused by changes in the speed of light as it passes from one medium to another, or through varying temperatures and densities of the same medium. This image shows what happens when a person sees a fish swimming in water. As you can see, the image shows how light from the sun and light from the fish are perceived differently to the eye.
Chapter 29 Section 9 - Atmospheric Refraction ~When atmospheric refraction occurs, there is a speeding up of the wave nearest to the ground and produces a gradual bending of the light rays.
These two pictures show the different ways the waves can be reflected.
mirage- a floating image that appears in the distance and is due to the refraction of light in the earth's atmosphere.
The above picture shows a representation of a mirage, or how it would be perceived.
Chapter 29 Secion 10 - Dispersion in a Prism
dispersion- the separation of light into colors arranged according to their frequency, by interaction with a prism or diffraction grating, for example.
dispersion is what enabled Isaac Newton to produce a spectrum!
This picture represents a simple dispersion through the a prism.
Chapter 29 Section 11 - The Rainbow ~The conditions for seeing a rainbow are that the sun be shining in one part of the sky and that water droplets in a cloud or in falling rain be in the opposite part of the sky.
~When you turn your back to the sun, you see the spectrum of colors in a bow.
The above image is the rainbow one would see if the ground weren't in the way! This image may also be seen from an airplane, but not very often.
This is an image of a single raindrop, showing how the light from the sun refracts into the drop then reflects producing the colors of the rainbow!~In a single raindrop, at the first refraction, the light is dispersed into its spectral colors. Violet is bent the most and red the least.
~The rays reach the opposite part of the drop to be partly refracted out into the air and partly reflected back into the water.
~The second refraction is similar to that of a prism, where refraction at the second surface increases the dispersion already produced at the first surface.
~Then, finally, each drop disperses a full spectrum of colors!
Chapter 29 Section 12 - Total Internal Reflection
critical angle - the minimum angle of incidence for which a light ray is totally reflected within a medium.
total internal reflection- the 100% reflection (with no transmission) of light that strikes the boundary between two media at an angle greater than the critical angle.
optical fibers- transparent fibers, usually of glass or plastic, that can transmit light down its length by means of total internal reflection.
they are also called light pipes
This picture shows how internal reflection works, within an optical fiber. As you can see by the arrows, the internal reflection isn't difficult to understand!
Practice Problems The following practice problems were assigned by Mr. Strong and are found in the textbook:
Sections:
Chapter 29 Section 1 - Reflection
The picture above represents the difference between the reflection of particles and the reflection of waves.
Chapter 29 Section 2 - The Law of Reflection
The above image shows how the law of reflection works. Such that, the angle of incidence=the angle of reflection.
Chapter 29 Section 3 - Mirrors
~ On a mirror rays of light are reflected from the mirror surface in all directions.
~ The number of rays is infinite, and every one obeys the law of reflection.
As described below the figures, these two images represent how light rays are affected when in context with a convex and concave mirror.
The above image shows how a virtual image works.
Chapter 29 Section 4 - Diffuse Reflection
- diffuse reflection- the reflection of waves in many directions from a rough surface.
~Reflection of each single ray obeys the law of reflection, the many different angles that incident light rays encounter cause reflection in many directions.~We see most of the things around us by diffuse reflection.
In the above image, light rays are hitting a rough surface and scattering in different directions. This represents diffuse reflection.
Chapter 29 Section 5 - Reflection of Sound
~An echo is reflected sound.
~Sound reflects from all surfaces of a room, such as: walls, ceiling, floor, furniture, and people.
The above figures, though already described underneath the pictures, represents reverberation in a room.
Chapter 29 Section 6 - Refraction
The above picture is a simple representation of how a refracted ray is refracted when hitting a different medium.
Chapter 29 Section 7 - Refraction of Sound
~On a warm day, the air near the ground may be appreciably warmer than the air above.
~Since sound travels faster in warmer air, the speed of sound near the ground is increased.
~Sound waves will then bend away warm ground, making it appear that the sound does not carry well.
~On a cold day or night, when the layer of air near the ground is colder than the air above, the speed of sound near the ground is reduced.
~The higher speed of the wave fronts above cause a bending of the sound toward the earth.
~When this happens, sound can be heard over considerably longer distances.
The above and below images show the way warm and cool air affect how sound travels.
Chapter 29 Section 8 - Refraction of Light
~A pond or swimming pool both appear shallower than they actually are.
~A pencil in a glass of water appears bent.
~Wonder why?
~These effects are caused by changes in the speed of light as it passes from one medium to another, or through varying temperatures and densities of the same medium.
This image shows what happens when a person sees a fish swimming in water. As you can see, the image shows how light from the sun and light from the fish are perceived differently to the eye.
Chapter 29 Section 9 - Atmospheric Refraction
~When atmospheric refraction occurs, there is a speeding up of the wave nearest to the ground and produces a gradual bending of the light rays.
These two pictures show the different ways the waves can be reflected.
The above picture shows a representation of a mirage, or how it would be perceived.
Chapter 29 Secion 10 - Dispersion in a Prism
This picture represents a simple dispersion through the a prism.
Chapter 29 Section 11 - The Rainbow
~The conditions for seeing a rainbow are that the sun be shining in one part of the sky and that water droplets in a cloud or in falling rain be in the opposite part of the sky.
~When you turn your back to the sun, you see the spectrum of colors in a bow.
The above image is the rainbow one would see if the ground weren't in the way! This image may also be seen from an airplane, but not very often.
This is an image of a single raindrop, showing how the light from the sun refracts into the drop then reflects producing the colors of the rainbow!~In a single raindrop, at the first refraction, the light is dispersed into its spectral colors. Violet is bent the most and red the least.
~The rays reach the opposite part of the drop to be partly refracted out into the air and partly reflected back into the water.
~The second refraction is similar to that of a prism, where refraction at the second surface increases the dispersion already produced at the first surface.
~Then, finally, each drop disperses a full spectrum of colors!
Chapter 29 Section 12 - Total Internal Reflection
This picture shows how internal reflection works, within an optical fiber. As you can see by the arrows, the internal reflection isn't difficult to understand!
Practice Problems
The following practice problems were assigned by Mr. Strong and are found in the textbook:
Pages 460-461 Review Questions #1, 3, 4, 5, 6, 8, 9, 11, 12, 15, 16, 17, 23, 24, 26
Pages 461-462 Think and Explain #1, 2, 5, 6, 8, 9, 10
Page 462 Think and Solve # 1, 2, 3
Sources